Mvc 3/Unity 2 inject dependencies into a Filter?

How can i inject the following dependencies ??

public class Authenticate : AuthorizeAttribute
{
        [Dependency]
        public IAuthenticate AuthenticateLibrary { get; set; }

        [Dependency]
        public ILibrary BaseLibrary { get; set; }

        protected override bool AuthorizeCore(HttpContextBase httpContext)
        {
        }
}

I am using Unity 2 to inject all the controllers. Is there a tutorial for Unity 2 and i开发者_如何转开发njecting dependencies into filters?

Brad Wilson has a good series on Service Location which includes how to create your own filter provider that can support dependency injection: http://bradwilson.typepad.com/blog/2010/07/service-location-pt4-filters.html (Scroll down to the section "Adding Dependency Injection to Filters").

• Copy the code he provides for the UnityFilterAttributeFilterProvider.cs.

UnitFilterAttributeFilterProvider.cs

using System.Collections.Generic;
using System.Web.Mvc;
using Microsoft.Practices.Unity;

public class UnityFilterAttributeFilterProvider : FilterAttributeFilterProvider {
    private IUnityContainer _container;

    public UnityFilterAttributeFilterProvider(IUnityContainer container) {
        _container = container;
    }

    protected override IEnumerable<FilterAttribute> GetControllerAttributes(
                ControllerContext controllerContext,
                ActionDescriptor actionDescriptor) {

        var attributes = base.GetControllerAttributes(controllerContext,
                                                      actionDescriptor);
        foreach (var attribute in attributes) {
            _container.BuildUp(attribute.GetType(), attribute);
        }

        return attributes;
    }

    protected override IEnumerable<FilterAttribute> GetActionAttributes(
                ControllerContext controllerContext,
                ActionDescriptor actionDescriptor) {

        var attributes = base.GetActionAttributes(controllerContext,
                                                  actionDescriptor);
        foreach (var attribute in attributes) {
            _container.BuildUp(attribute.GetType(), attribute);
        }

        return attributes;
    }
}

• Modify the Application_Start of the global.asax.cs to make the UnityFilterAttributeFilterProvider the filter provider for your MVC app.

.

protected void Application_Start() {
    // ...

    var oldProvider = FilterProviders.Providers.Single(
        f => f is FilterAttributeFilterProvider
    );
    FilterProviders.Providers.Remove(oldProvider);

    var container = new UnityContainer();
    var provider = new UnityFilterAttributeFilterProvider(container);
    FilterProviders.Providers.Add(provider);

    // ...
}

• Decorate the properties that you want Unity to inject a value for with the [Dependency] attribute. And then you should be good to go.

Since Unity is not instantiating the Filters, it cannot inject them. You would have to resort to service locator pattern such as in the following:

public class Authenticate : AuthorizeAttribute
{
    public IAuthenticate AuthenticateLibrary { get; private set; }

    public ILibrary BaseLibrary { get; private set; }

    public Authenticate()
    {
        AuthenticateLibrary = DependencyResolver.Current.GetService<IAuthenticate>();
        BaseLibrary = DependencyResolver.Current.GetService<ILibrary >();
    }
    ...
}

For all people that (like me) arrived here looking for a solution in MVC4 + Unity, although the accepted answers works perfectly, I wanted to add that now you can also simply override the GetFilters method of the FilterAttributeFilterProvider class:

public class CustomFilterProvider : FilterAttributeFilterProvider
{
    private readonly IUnityContainer container;

    public CustomFilterProvider(IUnityContainer container)
    {
        this.container = container;
    }

    public override IEnumerable<Filter> GetFilters(ControllerContext controllerContext, ActionDescriptor actionDescriptor)
    {
        var filters = base.GetFilters(controllerContext, actionDescriptor);

        var enumerable = filters as IList<Filter> ?? filters.ToList();

        foreach (var filter in enumerable)
        {
            container.BuildUp(filter.Instance.GetType(), filter.Instance);
        }

        return enumerable;
    }
}

Cheers.